Collaboration Agreements (Development And Commercialization Cost-Sharing Payments) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Development Cost Sharing Payments [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	$ 11,054	$ 13,964	$ 40,871	$ 42,980
Development Cost Sharing Payments [Member] | Astellas [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	11,003	11,480	39,131	32,593
Development Cost Sharing Payments [Member] | Pfizer [Member]
Collaboration Agreements [Line Items]
Development cost-sharing payments	51	2,484	1,740	10,387
Commercial Cost Sharing Payments [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(1,187)	173	(1,848)	667
Commercial Cost Sharing Payments [Member] | Astellas [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments	(1,187)	176	(1,857)	634
Commercial Cost Sharing Payments [Member] | Pfizer [Member]
Collaboration Agreements [Line Items]
Commercialization cost-sharing payments		$ (3)	$ 9	$ 33